1. Field of the Invention
The present invention relates to a memory control apparatus configured to control a plurality of storage devices.
2. Description of the Related Art
A conventional disk array system including a plurality of storage devices shares data stored on each storage device in order to handle failure that may occur on any storage device. Furthermore, various apparatuses, such as a data processing apparatus or an image processing apparatus uses a disk array system described above.
A conventional printing apparatus that uses a disk array system of this type executes the background processing on a relatively low priority basis, when print processing and background processing are executed in which the background processing is executed for purposes other than printing, by using a shared storage device, such that main processing (in this case, the print processing) is not affected, or within a fixed ratio of processing. However, depending on a content of such background processing, it may be necessary to execute the background processing on a priority basis higher than that of the main processing or to complete the background processing within shortest processing time to prevent the efficiency of the main processing from degrading.
In a mirroring (redundant array of independent disks (RAID1) system, which is intended to implement high data security, failure may occur on one hard disk drive (HDD). If one HDD has failed, the failed HDD is exchanged with a new HDD and a content of the data stored on the other normally functioning HDD is copied onto the newly mounted HDD. The copy processing described above is usually executed on background.
If the normally functioning HDD fails during the background processing, the data security function cannot work. In this case, data stored on the normally functioning HDD cannot be reproduced. Accordingly, in executing background processing to restore the apparatus from an abnormal state to a normal state as in the above-described case or the like, it is necessary to complete the processing as soon as possible.
Japanese Patent Application Laid-Open No. 2002-278704 discusses a method for determining a priority order of executing main processing and background processing based on information stored in a priority table, which stores priority information for executing main processing and background processing. However, in executing the method discussed in Japanese Patent Application Laid-Open No. 2002-278704, it is necessary to execute complicated operations for generating a priority table and registering the generated priority table on the storage device even when the number of background processing is not large.
In addition, in controlling the priority order based on information stored on the priority table that is registered on the storage device, it is necessary to execute complicated operations for determining the order of processing a plurality of given access requests on an access requesting apparatus. The above-described problem may arise as long as memory apparatuses are used that can be connected in an array similar to a case where an HDD is used as the storage device.